1. Field of the Invention
The present invention relates to a process for forming a resist pattern by thickening a resist pattern formed of, for example, an ArF resist to thereby easily form a fine resist space pattern (a resist pattern having a narrowed pitch) exceeding exposure limit of optical source of conventional exposure devices; a high-performance semiconductor device having a fine resist space pattern formed by using the resist pattern having a narrowed pitch which is formed by the above process; and an efficient process for fabricating the semiconductor device.
2. Description of the Related Art
With increasing packing densities of semiconductor integrated circuits, LSI and VLSI have been in practical use. A wiring pattern now reaches the range of less than 0.2 μm, and the minimum dimension is 0.1 μm or less. In order to form a fine wiring pattern, it is very important to take advantage of lithography. The lithography comprises the steps of applying a resist film to a substrate having a thin film(s), selectively exposing the resist film to light and developing the exposed resist film to form a resist pattern, dry-etching the thin film(s) by using the resist pattern as a mask, and removing the resist pattern to yield a desired pattern.
In order to form a fine wiring pattern, it is necessary both to shorten a wavelength of an optical source of an exposure device, and to develop a resist material which has a high resolution based upon properties of the optical source. However, in order to shorten the wavelength of the optical source of an exposure device, the exposure device must be renewed, which results in considerable expenses. Developing a resist material which suits an exposure with a shorter wavelength is not very easy.
A process of fabricating a semiconductor device includes forming a resist pattern having a fine opening, and then finely patterning a target article using the fine resist pattern as a mask. Therefore, the resist pattern should be preferably excellent in etching resistance. However, in the newest technique, an argon fluoride (ArF) excimer laser exposure, a resist pattern used for the exposure is insufficient in etching resistance. Demands have been made on techniques to form a resist pattern excellent in etching resistance, and to form a fine resist space pattern by using the resist pattern.
A technique called RELACS is described in Japanese Patent Application Laid-Open (JP-A) No. 10-73927, in which a fine space pattern can be formed by use of KrF excimer laser light (wavelength: 248 nm), deep ultraviolet radiation, as the exposure light for a resist. This technique comprises patterning a resist by exposing the resist (positive type or negative type) to the KrF excimer laser light (wavelength: 248 nm) as the exposure light, forming a film by use of a water-soluble resin composition so as to cover the resist pattern, making the film interact with the resist pattern at the interface by action of a residual acid in the material of the resist pattern to thicken (hereinafter often referred also to as “swell”) the resist pattern, thereby shortening the pitch between resist patterns to form the fine resist space pattern (pattern having a fine opening).
However, the KrF resist used in the technique is an aromatic resin composition such as a polyvinyl phenol resin. An aromatic ring contained in the aromatic resin composition highly absorbs the ArF excimer laser light. Therefore, the ArF excimer laser light cannot be used as the exposure light.
From the viewpoint of forming a fine wiring pattern, the ArF excimer laser light having a shorter wavelength than KrF excimer laser light should be preferably usable as an optical source in patterning.
However, a technique to form a fine pattern excellent in etching resistance easily with low cost, by using the ArF excimer laser light as an optical source of an exposure device in patterning has not yet been provided.
Objects and Advantages
Accordingly, an object of the present invention is to provide a process for thickening a resist pattern formed of, for example, an ArF resist to easily form a fine resist space pattern exceeding exposure limit of optical source of an exposure device; a high-performance semiconductor device having a fine pattern formed by the fine resist space pattern which is formed by the above process; and an efficient process for fabricating the semiconductor device.